PHOTOS: Unsightly algae invades reflecting pool

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It comes less than two weeks after the algae was discovered growing on the water, something that isn’t supposed to happen after the multimillion dollar renovation.

The algae was noticed at one end of the reflecting pool in late September. It almost completely covered the surface of the water.

The reflecting pool in front of the Lincoln Memorial on the National Mall reopened at the end of August after a two-year, $34 million reconstruction. It was the largest National Park Service project funded by President Barack Obama's economic stimulus package.

Before the renovation, the pool had stagnant water in it and had begun to leak and sink into the land.

Now, however, the pool has been re-engineered with a circulation and filtration system. Instead of using city drinking water, it draws river water from the nearby Tidal Basin, which will save 20 million gallons of drinking water each year.

But that’s where the problems stem from. The Park Service says the Tidal Basin water isn’t chemically treated. Instead, it’s treated with ozone. The level of ozone, however, needs to be adjusted to prevent the algae from forming, but tweaking the levels post-bloom and trying to skim it off wasn’t working fast enough.

“Because we didn’t have it right at the beginning, the algae established itself,” says Carol Johnson, spokesperson for the National Park Service. “Algae doubles in size every four hours so it is a formidable foe.”

The project included a new pool, landscaping, lighting and handicapped-accessible walkways. Algae wasn’t part of the deal, but most seem to take it in stride.

It will take two or three weeks and cost $100,000 on top of the multimillion dollar project that was pumped into the initial project.

“We do know that it’s a disappointment to the visitors who are here and are appreciating their patience, but we’re going to get this done as quickly as possible,” says Johnson.